Tumblrinas didn't exist back then and if you told a woman they were "healthy at every size" they'd laugh right in your face. Women back then took care of themselves.
According to the National Institute of Diabetes and Digestive and Kidney Diseases with data from 2013-2014, 40.4% of American women were obese, and 26.5% were overweight. So about 67% were fat then. I can't imagine that number got any smaller.